QTabWidget, Signal & Slot

Xavier59

Hi,

I have a QTabWidget with many page.
When the user is clicking on the first tab, I would like to update informations.
Moreover, I don't want to use a thread for it, to not overthread my applcation.

This is what I did :

 void MaFenetre::MaFenetre(): QWidget(){
     allTab = new QTabWidget(this);
     // Some things
     QObject::connect(allTab,SIGNAL(currentChanged(int)),this,SLOT(isChanged(int)));
 }

void MaFenetre::isChanged(int pos){
    if(pos == 0){
        this->updateMain();
    }
}

But this isn't doing what I want. I would like to change my tab, and then to execute the SLOT. This is doing the way.
Btw, I tryed also this, but this is giving the same result :

void MaFenetre::isChanged(int pos){
    if(pos == 0){
        allTab->setCurrentIndex(0);
        this->updateMain();
     }
}

Thanks.

SGaist

Hi and welcome to devnet,

What are the result you are expecting and what do you currently get ?

Xavier59

Hi,

I expect to change of tab, and then, to update the page.
At the moment, when I click on my tab, it is updating the tab, and then, changing the tab.

TheBadger

Perhaps use a timer to delay the updating:

void MaFenetre::isChanged(int pos){
    if(pos == 0) {
        QTimer::singleShot(200, this, &MaFenetre::updateMain);
    }
}

SGaist

There's some kind of strange loop here.

Basically, when allTab has its index changed to 0, you set it to 0 again, and then call updateMain. What is the purpose of allTab in MaFenêtre ?

Xavier59

@TheBadger said:

Perhaps use a timer to delay the updating:

void MaFenetre::isChanged(int pos){
    if(pos == 0) {
        QTimer::singleShot(200, this, &MaFenetre::updateMain);
    }
}

Thanks a lot, This solution worked fine for me !

@SGaist said:

There's some kind of strange loop here.

Basically, when allTab has its index changed to 0, you set it to 0 again, and then call updateMain. What is the purpose of allTab in MaFenêtre ?

The fact is that it wasn't changing my tab until updateMain(); finished. As my function take some time to be executed (2-3 seconds) when I was clicking on the index 0, i had a delay of 2-3 seconds before it switched to this tab.

SGaist

Should that updating happen only before that tab is shown ?

Xavier59

@SGaist said:

Should that updating happen only before that tab is shown ?

Kind of. It's useless to update it while the user don't want to see them.

SGaist

In that case why not trigger it through the showEvent of your widget ?

What makes that update take so much time ?

Xavier59

I apologize for the delay.
I'm downloading a picture during the update, that's why it is taking so much time.
Of course, I could do a QThread, but I try to use them as less as possible to not over thread.

SGaist

Are you downloading it each time ?

Xavier59

Yes, I want to download it again each time I'm back on my update tab.

SGaist

In that case why not add a spinner or busy indicator and show the widget directly ? It will at least remove the feeling that your application is stuck.